1. Field
The invention relates to injection blow molding machines and, more particularly, to improvements in heat transfer throughout a nozzle of the injection blow molding machine.
2. Discussion of the Related Art
A parison molding cavity at an injection molding station of a typical injection blow molding machine is formed in part by a pair of superimposed mold halves that split or separate along the center line of each gate opening and parison cavity. Hot melt injection nozzles have discharge tips that are seated in the gate openings. To remove a set of newly formed parisons from the mold, the upper mold halves are raised off the bottom mold halves, and the cores that carry the new parisons are then lifted and rotated out of the mold. A new set of cores is placed in the cavities of the bottom mold halves and the mold is closed, creating a diametrical sealing relationship between each nozzle tip and the wall of its gate opening and preparing the mold cavities to receive hot melt through the nozzles.
Each nozzle is coupled, at its base, with a resin manifold. Prior to performing the injection blow molding, the manifold is heated to a desired operating temperature. Hot melt is supplied to each nozzle at the nozzle's base from a resin source associated with the manifold. The resin then flows through the nozzle and to the parison mold. The resin is heated to a beginning operating temperature from the heat supplied by the manifold via thermal conduction through the nozzle base. However, the resin quickly begins to cool as it flows through the nozzle, as the nozzle progressively cools along its axial length forward of the manifold. To maintain the resin at a sufficient operating temperature along the entire length of the nozzle, prior art nozzle injection systems employ an external heat source, such as a heater or a torch. The external heat source warms the nozzle, which in turn heats the resin. Although the external heat source insures the resin stays at a sufficient operating temperature, use of the external heat source increases the cost of the injection blow molding process and is a potential source of breakage and malfunction.
Accordingly, there is a need for an injection nozzle and injection blow molding system that is operable to maintain the resin at a sufficient operating temperature along the entire length of the nozzle without use of an external heat source.